You should just be able to unzip the game and run the executable. You'll get a configuration screen where you can change the graphics quality and input settings - just press "Play!" to start. After that you'll see two dominoes drop onto a table. Use the arrow keys or WASD to control one of them, or the left stick of your gamepad. More players can join using more gamepads. A full control map is included in the zip file, and is also shown in-game if you press Escape.